Wide dynamic range amplifying and demodulating system



July 18, 1950 w. R. BLISS 2,515,187

WIDE DYNAMIC RANGE AMPLIF'YING AND DEMODULATING SYSTEM Filed Apri/l 9, 1942 A? VIDEO IIVPl/T OUTPUT gamma tow n l'llz'am R. Bliss m Ww Patented July 18, 1950 Winn DYNAMICRANGE nMPmimi-Ne IAND DEMODULATING SYSTEM w'maa'aselss, wit-stages; 'nfc. Application April 9, 1942;serm1 No. 438. 320 s claiiiis. (011550 20) (Granted under "the act of March:3,-:=18-83, as

amended April 30, 1928;"370 G. 757) This invention relates to an' 'amplify'ing and uineduiatin system for use in 'radio reception Midktalflable"of' flllicti0r1ing over a wide dynamic rangew'ithout' blocking. Whenever us'ed herein. the temsuynamic range and dynamic level refer 'respe'ctively'to range andlevel of signal strength.

"I'liedriventibndihds particular appl'ioation to radiocho'distance'finding systems as a means for preventingthe jamming of receivers by the use of fi'lw 'sign'als.

It is an' obiect'o'f this invention to provide an amplifying and demodulating system for use in radio' reception "which" will give unimpaired response and substantially uniform gain over a wide dynamic rangof signal reception.

It-is another object ofthis invention to provide a system as indicated above which will, upon the blocking of the normal amplifying channel, make available analternative path of the same nature whichis normally unresponsive. a

is' 'a further object of'this inventionto proe an a"" plifying anddemodulating system hava series of amplifying and demodulating 'nnf'ls eafch originatin'g'ahea'd of a different sim'cauon stage of the normal-"amplifying and tfeniodulating channel and each becoming 'responsive only upon the reception of a signal of sufiicient amplitude to block the normal amplifying stage immediately following it. Other objects will become apparent from a careful consideration of the following description when taken together with the accompanying drawing, in which:

Fig. 1 is a block diagram of an amplifying and demodulating system embodying the invention, and

Fig. 2 is a schematic circuit diagram of a slightly modified version of the system illustrated in Fig. 1.

Referring now to Fig. 1 there is shown an amplifying and demodulating system comprising three stages of I. F. amplification designated by the reference characters I0, I l and I2 followed by the detector I3 and a stage I4 of video or audio amplification. Shunted around the last I. F. stage I2 and detector I3 is a detector I5 and a stage I6 of video or audio amplification. Shunted around the last two stages of I. F. amplification I I and I2 and the detector I3 is a detector I1 and the stages I8 and I6 of video or audio amplification, The gain of each of the three stages of the I. F. amplification and the video amplifiers I5 and I8 is preferably equal. The lower end of the efficient operating range of each of the detectors I5 and I1 is selected to lie at substantially the same dynamic level which will cause blocking of the stage 66 of amplification immediately flillowin the point atfi'which the detec'tor isconne'cted iit'o "the I: F. amplifyingsys'tem.

Irio'rdcr to "facilitate the matchingof the ga'm of the substituted videoampIification' With that of the corresponding 'I.F. stages, the detector I5 is shown in Fig. '2 connected ahead- GE the' ainpH firs "I S and I8 through an attenuator composed ofthe' "resistances R1 and R2 and Rsf-whi'clicon *s'titute a potentiometer. Matching'of gain may be accomplished by adjusting the value Of'Rl. ine. 2-- otherwise is*a schematic' 'cir'cuit 'diagram of tlie systems shown -in-Fig; 1= and is composed 'of coii -v'entional elements, "the descripti'onbf "which is not necessary. I

operation of "the device mas-follows:

"During --"the reception "of sigrials of n rinal strength eachof'the' detectors"l5:aiid I has s- .plied -to'it'an -input of suchlow value"as'-:to e" -low-its=eiiicient operating range. If'now a-si rial ibe rec eivedat such a dynamiolevel as :to bloc "he I. F; amplifier I2 the'inputtmdetector I5"w-ill li"e within its operating range and the tube-"will commence tofunction in an efficient manner. The stage "I6 of video amplification will 'rpla" iie stage I {of I5 F."'amplification which zhas'been reiidered inoperative. If the dynamic level of the signal is raised sufficiently so as also to block stage II of I. F. amplification the detector I! will commence to function and the stage I8 of video amplification Will replace stage I I. Thus the gain is. kept constant but the dynamic range is greatly in-- creased. Use of the attenuator shown in'Fig. 2 will also operate to maintain constant the gain of the system regardless of whether one or two stages of I. F. amplification have been blocked.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. An amplifying and demodulating system comprising a main channel, said main channel comprising at least one amplifying stage followed by a demodulator, and a branch channel shunted around said amplifying stage and said demodulator and returning to said main channel, said branch channel comprising a demodulator followed by at least one amplifying stage, the lower limit of the operating range of the demodulator of said branch channel beginning at substantially the dynamic level at which the amplilying stage of said main channel blocks.

coupling the output of the amplifier to the sec- 0nd rectifier; attenuation means fed by the secbranch circuits, each connected ahead of one of said amplifying stages and by-passing said demodulator and all of said amplifying stages following its point of connection, each of said comprising a main channel, said main channel comprising a plurality of cascaded amplifying stages followed by a demodulator, a second channel shunted around at least one of said amplifying stages and said demodulator, said second channel comprising a demodulator followed by at least one amplifying stage, the lower limit of the operating range of the demodulator in said secondchannel lying substantiall at the dynamic level at which occurs blocking of the main channel amplifying stage next following the point of attachment of said second channel.

5. ,A demodulation system comprising a main demodulation channel, said main channel comprising a plurality of amplification stages, a plurality of branch demodulation channels shunting said main channel, each of said branches originating ahead of a different one of said stages,

I and having a dynamic operating range the lower limit of which coincides with the upper limit of the dynamic operating range of the amplification stage next following it point. of origin.

6. In combination, input means; a first rectifier fed by the input means; an amplifier fed by the input means; a second rectifier; means 0nd rectifier; output means coupled to the first rectifier and the attenuation means; and means operative to apply a modulated alternating signal to the input means.

. 7. In combination, inputmeans;;. xmeans operative to apply to the input means a modulated alative to render the first signal channel responsive only to signals above a predetermined level of amplitude; a second signal channel fed by the input means comprising an amplifier, a second rectifier fed by the amplifier, and a linear attenuator fed by the second rectifier, the second signal channel being responsive only to signals below a predetermined level of amplitude; and output means operative to combine signals derived from the first signal channel and the second signal channel. 7 H

8. In combination, signal channel means for carrying signals of Widely varying amplitudes, detector means operative to rectify low levelsignals responsive to the signal channel means, fur1- ther detector means operative to rectify higher level signals responsive to the signal channel means, output channel means responsive to both said detector means, and attenuator meansoperatively interposed between the lower level; detector means and the output channel means.

Number Name 1,477,017 Sprague Deo.;1l, 1923 1,711,658 Sprague Mayp'k 1929 1,808,915 Bjornson June 9, 1931 2,014,509 Roosensteinet al. Sept.,1'7,. 19 35 2,031,072 Roosenstein Feb. 18,1936

2,269,011 DallOS Jan. 6,11%? 

